CDC reports increase in flu activity, plus one swine H3N2 flu case

Sep 4, 2009 (CIDRAP News) – The US Centers for Disease Control and Prevention (CDC) today reported an increase in pandemic H1N1 flu activity in the nation, focused primarily in five southeastern states, along with an isolated case of swine H3N2 influenza in a patient from Kansas.

Officials from the CDC have said they expect flu activity to pick up again when students return to school, and many districts in the southeast resumed classes on Aug 10.

Seasonal H1N1, H3N2, and B influenza viruses are circulating at low levels, but the pandemic H1N1 virus accounted for 97% of all flu viruses that were subtyped.

As of today, 9,079 hospitalizations and 593 deaths have been linked to the pandemic H1N1 virus. Nine cases of oseltamivir-resistant novel H1N1 influenza have been detected in the United States, which is two more than the previous week.

Alaska also reported widespread flu activity for the week ending Aug 29. Thirteen states, including six in the southeast, reported regional activity. The CDC said the number of outpatient visits for influenza-like illnesses rose but was still below the national baseline. Much of the rise was attributed to clinic visits for flu in southeastern states.

The CDC also reported a human infection with a swine influenza A/H3N2 virus, a patient from Kansas who had contact with pigs before getting sick on Jul 28.

The patient is a child who was likely exposed to the virus through direct contact with pigs during a county fair, the Kansas Department of Health and Environment (KDHE) said in an Aug 6 news release. The illness was mild, the child has fully recovered, and no other family members reported symptoms.

H1N1 and H3N2 swine flu viruses are endemic in US pig populations; when the rare infections do occur in humans, they are typically in people with direct exposure to pigs. The number has risen slightly in past years, and so far this year the CDC has received reports of 14 such cases. The KDHE said the increased number of cases this year is probably the result of increased influenza testing related to the H1N1 pandemic.

Jason Eberhart-Phillips, MD, MPH, director of the KDHE, said it's critical for people to understand that the H3N2 virus is not related to the pandemic H1N1 virus. "This is not a mutation or a recombination of the pandemic strain, and it does not appear at this time to be a threat to human health," he said in the press release.

Though most cases of human infection with animal influenza viruses, such as swine H3N2, don't lead to human-to-human transmission, health officials always investigate the cases carefully to assess if they are spreading among humans, Eberhart-Phillips said.